1. Technical Field of the Invention
The present invention relates in general to the mobile radio communications field and, in particular, to a method and system for recovering from cell outages in a mobile radio communications network.
2. Description of Related Art
From time to time, the radio coverage for one or more cells in a cellular network has to be restored. For example, a cell can be made inoperative because of a software or hardware failure in a base station or transceiver unit that creates and defines that cell. As such, in order to minimize the negative impact on network traffic due to these inoperative cells, it is an important network objective to restore service in these cells in an optimum manner.
Typical network switching systems where such cell outages occur are in mobile services switching centers (MSCs) or radio network controllers (RNCs). Currently, only a relatively small number of these switching systems can control up to a few hundred cells at a time, which essentially has limited the negative impact of the inoperative cells, and thus, the extent of the recovery required. However, as vendors are now producing much higher-capacity switches (e.g., capable of controlling several hundred cells/transceivers), the problem of how to optimally restore service for the potentially much larger numbers of inoperative cells poses a more difficult design challenge.
A number of existing and planned network cell recovery techniques are optimized for greater coverage. In other words, during the initial recovery phase, only one or a few channels are brought into service in each cell. During the next phase, more channels are restored in each cell, and so on, until the cell recovery operation is complete. As such, this gradual recovery approach works adequately during low traffic periods (e.g., at night). However, this gradual recovery technique is much less effective during periods of high traffic, or when a number of the cells differ in terms of traffic demand and/or general importance.
Other existing and planned network cell recovery techniques are based on prioritization of the cells. In other words, some (e.g., higher priority) cells are restored more or less completely, and then the lower priority cells are restored. This priority recovery technique is less effective during low traffic periods (typically when most cell recovery operations are scheduled). For example, there is little point in restoring 40 channels per cell during the night (low traffic period). This shortcoming of the priority recovery technique becomes more evident, if for example, an emergency call cannot be processed in a lower priority cell which has not yet been restored. Essentially, the existing and planned network cell recovery techniques afford less network availability than operators require. However, as described in detail below, the present invention successfully resolves these problems.